Properties, synthesis, and characterization of graphene

Graphene is a wonder material that attracts great interests in materials science and condensed matter physics. It is the thinnest material and also the strongest material ever measured. Its distinctive band structure and physical properties determine its bright application prospects. This review introduces briefly the properties and applications of graphene. Recent synthesis and characterization methods are summarized in detail, and the future research direction is also pointed out in this paper.     

钙钛矿型钛酸锶的制备、结构与性能

钛酸锶是一种具有重要电性质的陶瓷材料 ,因而在工业上得到了广泛的应用。本文介绍了钛酸锶的几种常见的合成方法 ,并简要的介绍了钛酸锶的结构与性能     

Development of semi-empirical formulation for extracting materials properties from nanoindentation measurements: Residual stresses, substrate effect, and creep

Nanoindentation is one of the most popular techniques for characterizing the mechanical properties of micro- or nano-structured metals or dielectric thin films. However, the obtained experimental data can only provide the relationship between the applied load and the penetration depth. Mechanics models are therefore required to convert the test data into the corresponding material properties. In this work, the effect of residual stress, the substrate effect, and the creep of materials subjected to the indentation test are discussed in order to establish appropriate conversion formulas or criteria for extracting the interested material properties. Dimensional analyses are firstly performed to find the governing parameters and to obtain scaling relationships for subsequent finite element analysis. With the described procedure, models have been developed to convert nanoindentation test data into the desired material properties. Those models provide useful tools for extracting specific material properties, such as residual stress, creep exponent, and stress relaxation time constant. Specifically, this investigation also shows that for the situation of soft film/hard substrate combination, the indentation behavior is essentially identical if the modulus of the substrate is 10 times higher than that of the corresponding film and the response deviates consistently from that of bulk material with increasing of indentation depth. For penetration depth less than 10% of the film thickness, the deviation could be acceptable. On the other hand, significant deviation is observed for hard film/soft substrate systems. In summary, by integrating the models proposed by this work and data from standard tests, it is possible to obtain the Young's modulus, hardness, and the viscoelastic properties as well as the residual stress for a specific material through indentation characterization.     

316L不锈钢、铜、锡复合框架材料研究

设计并采用电刷镀复合工艺制造了一种316L不锈钢、铜、锡复合框架功能材料，此功能材料具有良好的弹性、导电、导热性能和优异的钎焊性能，且无磁性，可满足某大型机组控制系统的要求，同时对此材料的组织性能等进行了研究。     

Effect of Active Raw Material Variability on Tablet Production: Physicochemical, Physiocomechanical and Pilot Plant Studies

Batch-to-batch variation in an active raw material was evaluated following a production process change by the raw material supplier. Physicochemical and physicomechanical tests were applied and indicated that polymorphism or solvate formation was not occurring but changes in crystal properties in terms of size and degree of aggregation were involved. Other more subtle differences in crystal properties were also possible

The deleterious effect of the raw material process change on tablet production was noted and a method of overcoming the problem identified

The necessity for comprehensive? reformulation studies including physicomechanical screening is underlined. Such studies are also necessary if changes in raw material production methods occur to avoid process problems related to the marked hatch-to-batch variation that can occur in these instances     

Carbon Dot-Based Hydrogels: Preparations,Properties, and Applications (Small 17/2023)

Hydrogels have extremely high moisture content, which makes it very soft and excellently biocompatible. They have become an important soft material and have a wide range of applications in various fields such as biomedicine, bionic smart material, and electrochemistry. Carbon dot (CD)-based hydrogels are based on carbon dots (CDs) and auxiliary substances, forming a gel material with comprehensive properties of individual components. CDs embedding in hydrogels could not only solve their aggregation-caused quenching (ACQ) effect, but also manipulate the properties of hydrogels and even bring some novel properties, achieving a win–win situation. In this review, the preparation methods, formation mechanism, and properties of CD-based hydrogels, and their applications in biomedicine, sensing, adsorption, energy storage, and catalysis -are summarized. Finally, a brief discussion on future research directions of CD-based hydrogels will be given.     

Randomly reinforced composites: properties, failure and aspects of material design

This article concerns several aspects of mechanical properties and tensile failure of randomly reinforced, chopped fiber strand, polymeric composites. Scatter in material properties and their dependence on sample size are investigated by means of an analytical/computational model and compared against the experimental data. Predictions are also provided for deviations from isotropy and homogeneity. Failure is modeled in a manner akin to the methodology employed for laminated composites and predictions are compared against the experimental data. The model is utilized to select combinations of multi-size strands so as to minimize material inhomogeneity.     

苯氧基取代度对聚膦腈材料性能的影响

对苯氧基取代程度对材料力学性能和热力学性质的影响进行研究。研究结果表明,P-O-P交联体系可以使材料获得良好的力学性能和耐烧蚀性能。实验表明,当取代度为85%左右时,材料具备良好的拉伸断裂强度和断裂伸长率,以及良好的耐烧蚀性能(36.7%残碳比例)。该研究还克服了传统上未完全取代聚磷腈材料无法使用这一技术偏见。研究表明,取代度较高的苯氧聚磷腈溶液是稳定性的,并且可以浇注成需要的形状。使该类材料获得了使用价值,而且其在使用过程中可以与环境中的水反应交联使材料获得日渐优异的力学和阻燃性能。     

Effect of Active Raw Material Variability on Tablet Production: Physicochemical,Physiocomechanical and Pilot Plant Studies

Abstract

Batch-to-batch variation in an active raw material was evaluated following a production process change by the raw material supplier. Physicochemical and physicomechanical tests were applied and indicated that polymorphism or solvate formation was not occurring but changes in crystal properties in terms of size and degree of aggregation were involved. Other more subtle differences in crystal properties were also possible

The deleterious effect of the raw material process change on tablet production was noted and a method of overcoming the problem identified

The necessity for comprehensive? reformulation studies including physicomechanical screening is underlined. Such studies are also necessary if changes in raw material production methods occur to avoid process problems related to the marked hatch-to-batch variation that can occur in these instances     

Remote, local, and chemical programming of healable multishape memory polymer nanocomposites

We show that the combination of remote, local, and chemical programming of the multishape memory effects offers unparalleled shape and function control in carbon nanotube-Nafion composites. This strategy not only allows the high-fidelity encoding and extraction of designed material shapes at different length scales (macro, micro, and nano) but also enables the reversible tunability of material functions, such as shape memorizability, mechanical properties, surface hydrophobicity, and material resealability, in a single nanocomposite.     

Tailoring nanostructured, graded, and particle-reinforced Al laminates by accumulative roll bonding

Accumulative roll bonding (ARB) is a very attractive process for processing large sheets to achieve ultrafine-grained microstructure and high strength. Commercial purity Al and many Al alloys from the 5xxx and the precipitation strengthened 6xxx alloy series have been successfully processed by the ARB process into an ultrafine-grained state and superior ductility have been achieved for some materials like technical purity Al. It has also been shown that the ARB process can be successfully used to produce multi-component materials with tailored properties by reinforcement or grading, respectively. This allows optimizing the properties based on two or more materials/alloys. For example, to achieve high corrosion resistance and good visual surface properties it is interesting to produce a composite of two different Al alloys, where for example a high strength alloy of the 5xxx series is used as the core material and a 6xxx series alloy as the clad material. It has been shown that such a composite achieves more or less the same strength as the core material although 50% of the composite consists of the significant softer clad alloy. Furthermore, it has been found, that the serrated yielding which typically appears in 5xxx series alloys and limits applications as outer skin materials completely disappears. Moreover, the ARB process allows many other attractive ways to design new composites and graded material structures with unique properties by the introduction of particles, fibres and sheets. Strengthening with nanoparticles for example is a very attractive way to improve the properties and accelerate the grain refining used in the severe plastic deformation process. With an addition of only 0.1 vol.-% Al2O3 nanoparticles a significantly accelerated grain refinement has been found which reduces the number of ARB passes necessary to achieve the maximum in strength. The paper provides a short review on recent developments in the field of ARB processing for producing multicomponent ultrafine-grained sheet materials with tailored properties.     

太阳能级硅中轻质元素(C,N,O)研究进展

C,N,O等轻质元素的存在对太阳能级晶体硅材料的性能有着广泛影响,而硅材料作为太阳能电池的主要原材料,其纯度对电池的电学性能有着决定性作用。本文总结了晶体硅中C,N,O元素的存在形态、分布规律、形成机制及工艺控制等的研究进展,并对未来硅中轻质元素的研究进行了展望,使用各种提纯工艺的优势交叉互补来控制及去除硅中的杂质值得研究及关注,对硅中C,N,O元素的交互作用的深入研究也将会对硅材料质量的提高有着积极作用。     

Liquid Crystals for Charge Transport,Luminescence, and Photonics

Ordered molecular materials are increasingly used in active electronic and photonic organic devices. In this progress report we discuss whether the self‐assembling properties and supramolecular structures of liquid crystals can be tailored to improve such devices. Recent developments in charge‐transporting and luminescent liquid crystals are discussed in the context of material requirements for organic light‐emitting devices, photovoltaics, and thin film transistors. We identify high carrier mobility, polarized emission, and enhanced output‐coupling as the key advantages of nematic and smectic liquid crystals for electroluminescence. The formation of anisotropic polymer networks gives the added benefits of multilayer capability and photopatternability. The anisotropic transport and high carrier mobilities of columnar liquid crystals make them promising candidates for photovoltaics and transistors. We also outline some of the issues in material design and processing that these applications demand. The photonic properties of chiral liquid crystals and their use as mirror‐less lasers are also discussed.     

悬浮石墨烯的制备、性能及应用研究

作为一种新型二维材料,石墨烯在电学、光学、传热学及力学性能等方面均表现出极其优异的特性,对石墨烯的研究也得到众多研究者的关注.同时,拥有桥状悬浮结构的悬浮石墨烯(Suspended graphene)以其杂质少、受外界干扰小等优点使得石墨烯的本征特性得到最大化施展.在研究石墨烯的电子迁移率、传热性、力学性能等方面,悬浮石墨烯有着独特的优势,并且对提升微电子器件的性能作用显著.综述了悬浮石墨烯的制备与性质研究及其在微电子领域的应用进展,并展望了悬浮石墨烯的应用前景.     

Sol–gel synthesis, comparative characterisation, and reliability analyses of undoped and Al-doped zinc oxide thin films

Thin films of sol–gel derived undoped and Al-doped zinc oxide material systems were fabricated for potential use in transparent conducting oxide modules. A comparative characterisation of the functional properties of the films was performed. Undoped zinc oxide thin films were obtained with desired properties. Al doping reduced the average crystallite size, and led to a denser and less porous morphology, and also caused an increase in transparency in the UV region. An improvement in electrical conductivity was achieved upon Al doping. Temperature cycling and accelerated delamination test results demonstrated the high physical reliability of the thin films of the material system obtained in this study.     

Mechanogenomic coupling of lung tissue stiffness,EMT and coronavirus pathogenicity

In this Current Opinion, we highlight the importance of the material properties of tissues and how alterations therein, which influence epithelial-to-mesenchymal transitions, represent an important layer of regulation in a number of diseases and potentially also play a critical role in host-pathogen interactions. In light of the current SARS-CoV-2 pandemic, we here highlight the possible role of lung tissue stiffening with ageing and how this might facilitate increased SARS-CoV-2 replication through matrix-stiffness dependent epithelial-to-mesenchymal transitions of the lung epithelium. This emphasizes the need for integrating material properties of tissues in drug discovery programs.     

Kohlenstoffasern – Herstellung,Eigenschaften, Verwendung

Carbon Fibres – Production, Properties and Applications Carbon fibres are primarily regarded as a reinforcing material for resins, but can also be used in metal or carbon matrices. It is anticipated that over the next few years the present inception phase will develop into one of rapid business growth. The expected turnover and price developments, as well as the main fields of application are discussed. A great variety of carbon fibre types are available, whose properties are dictated by differences in the basic structure, yielding an exceptional range of properties from the isotropic low modulus to the high strength, high modulus, highly anisotropic HT and HM carbon fibres. The method of manufacture and the precursor materials are described, in particular the individual processing steps and changes accompanying the pyrolysis of PAN fibres. Future improvements in processing technology and precursor quality, promise a significant increase in the already very high properties level.     

Magnetic Anisotropies and (Ga,Mn)As‐based Spintronic Devices

In this Review, we discuss the rich anisotropic properties of the ferromagnetic semiconductor (Ga,Mn)As, and their implications in transport studies. We review the various sources and types of anisotropy seen in the material, discuss its magnetization reversal process, and demonstrate how basic transport properties, such as resistivity and Hall measurements, can be used as very sensitive tools to investigate the magnetization properties of the material. We also discuss how the magnetic anisotropy, coupled with large spin–orbit coupling, leads to an anisotropy in the transport density of states, which in turn leads to fundamentally novel behavior such as tunneling anisotropic magnetoresistance (TAMR).     

Metallische Werkstoffe — Eigenschaften,Verarbeitung, Anwendung in der Konstruktion

Metallic materials, properties, treatment, application in constructions . The main purpose of material research is to improve the properties of metals. Therefore it is necessary to study the influence of production, machining and construction on the properties of structural parts.     

Integrating concepts of material mechanics,ligand chemistry,dimensionality and degradation to control differentiation of mesenchymal stem cells

The role of substrate mechanics in guiding mesenchymal stem cell (MSC) fate has been the focus of much research over the last decade. More recently, the complex interplay between substrate mechanics and other material properties such as ligand chemistry and substrate degradability to regulate MSC differentiation has begun to be elucidated. Additionally, there are several changes in the presentation of these material properties as the dimensionality is altered from two- to three-dimensional substrates, which may fundamentally alter our understanding of substrate-induced mechanotransduction processes. In this review, an overview of recent findings that highlight the material properties that are important in guiding MSC fate decisions is presented, with a focus on underlining gaps in our existing knowledge and proposing potential directions for future research.